The present disclosure relates to an apparatus for generating a driving signal.
A touchscreen device, such as a touchscreen or a touch pad, is a data input device attached to a display device so as to provide an intuitive user interface, and has recently been widely used in various electronic devices such as cellular phones, personal digital assistants (PDA), and navigation devices. Particularly, as demand for smartphones has recently increased, touchscreens have increasingly been employed as devices allowing for various methods of data input in a limited form factor.
Touchscreens used in portable devices may be mainly divided into resistive type touchscreens and capacitive type touchscreens, depending on the manner in which touches are sensed. Among these, the capacitive type touchscreen has advantages of a relatively long lifespan and the ease of implementing various input manners and gestures, and thus it has been employed more and more. The capacitive type touchscreen is especially easy to implement a multi-touch interface compared to the resistive type touchscreen, and thus it is widely used in smartphones and the like.
The capacitive type touchscreen includes a plurality of electrodes having a predetermined pattern and the electrodes define a plurality of nodes at which a change in capacitance is generated due to a touch. In the plurality of nodes arranged on a two-dimensional plane, changes in self-capacitance or changes in mutual-capacitance are generated by touches, and coordinates of such touches may be calculated by applying, for example, a weighted average method to the changes in capacitance generated in the plurality of nodes.
Recently, touchscreen devices may detect touches proximate to a cover lens, as well as touches made directly to such a cover lens. A driving circuit, generating driving signals to be applied to a plurality of electrodes, applies different levels of driving signal when detecting a normal touch and when detecting a proximity touch causing minute changes in capacitance. In the case of having driving signals of different levels applied thereto, however, transistors having a low withstand voltage for generating a driving signal having a low voltage level may be disabled.
Further, touchscreen devices have recently been provided with a number of panels having various sizes, and noise may be introduced in the case of a large touch panel, as opposed to a small touch panel, so that it may be difficult to accurately detect touches. To overcome this, a large driving signal may be applied for driving the large touch panel. However, if a large driving signal is applied to a small touch panel, current consumption may be increased.